Band structure and micro gas turbine having the same

ABSTRACT

Disclosed are a band structure and a micro gas turbine having the same. An insert wall and a nozzle ring casing are respectively surrounded in part by a first band structure of a heat resistant material and a second band structure of a material that is identical or similar to the material of the first band structure to prevent thermal deformation of the insert wall and of the nozzle ring casing and a nozzle vane so as to maintain constant gaps between a blade tip of a turbine wheel and the insert wall and between a leading edge of the turbine wheel and the nozzle vane, thereby preventing reduction in both the power output of the turbine wheel even after a prolonged drive period and the operation efficiency of the micro gas turbine.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates, in general, to a band structure and a micro gas turbine having the same. More particularly, the present invention relates to a band structure, in which an insert wall and a nozzle ring casing are respectively surrounded in part by a first band structure of a heat resistant material and a second band structure of a material that is identical or similar to the material of the first band structure to prevent thermal deformation of the insert wall and of the nozzle ring casing and a nozzle vane so as to maintain constant gaps between a blade tip of a turbine wheel and the insert wall and between a leading edge of the turbine wheel and the nozzle vane, thereby preventing reduction in both the power output of the turbine wheel even after a prolonged drive period and the operation efficiency of a micro gas turbine, and a micro gas turbine having the same.

2. Description of the Related Art

A gas turbine is a rotary power engine that extracts energy from combustion gas flow. In the gas turbine, compressed air and fuel are mixed and then combusted so that high temperature and high pressure gas expands to drive a turbine. The energy is transmitted in a torque via a shaft, or is obtained in a type of thrust or compressed air. In order to obtain target drive efficiency of a turbine, a gap between a turbine and a nozzle vane and between the turbine and an insert wheel should be maintained at a proper level.

A micro gas turbine is a gas turbine that is made smaller from a conventional gas turbine. The output ranges from less than a kilowatt to hundreds of kilowatt. Such a micro gas turbine is being developed and becomes widespread in distributed power and combined heat and power applications due to its technical advantages and eco-environmental features.

FIG. 1 is a detailed front view showing a core of a conventional micro gas turbine, and FIG. 2 is a detailed cross-sectional view of the core of the conventional micro gas turbine.

Referring to FIG. 2, a nozzle ring casing 1 is formed from one-piece body that consists of a nozzle vane 5 which applies an aerodynamic force from a combustor 3 to a turbine wheel 4 while weight thereof is supported by a bearing casing 2, and an insert wheel 6 which serves as a channel wall of combustion gas passing through blades of the turbine wheel 4.

FIG. 3 is a heat-distribution chart showing the thermal-deformation directions at the core of the conventional micro gas turbine, and FIG. 4 is a partially enlarged view explaining the thermal-deformation directions.

By the high temperature combustion gas from the combustor 3, the insert wheel 6 and the nozzle vane 5 of the nozzle ring casing 1 are thermally deformed and enlarged in the direction denoted as arrow shown in FIG. 3.

Such thermal deformation and resulting enlargement cause both a gap A between a blade tip of the turbine wheel 4 and the insert wall and a gap B between the nozzle vale 5 and a leading edge of the turbine wheel to be excessive, resulting in the reduction in the power output of the turbine wheel and therefore reduction in the operation efficiency.

SUMMARY OF THE INVENTION

Accordingly, the present invention has been made keeping in mind the above problems occurring in the related art, and the present invention is intended to propose a band structure which maintains constant gaps between a blade tip of a turbine wheel and an insert wall and between a leading edge of the turbine wheel and a nozzle vane to prevent reduction in both the power output of the turbine wheel even after a prolonged drive period and the operation efficiency of a micro gas turbine, and a micro gas turbine including the same.

In order to achieve the above object, according to one aspect of the present invention, there is provided a band structure which surrounds a portion of an outer circumference of an insert wall or a nozzle ring casing in a micro gas turbine so as to prevent the insert wall or the nozzle ring casing from being enlarged due to thermal deformation.

In another aspect, the present invention provides a micro gas turbine including: a turbine wheel; a bearing casing provided in one side of the turbine wheel; a nozzle ring casing supported by the bearing casing; a combustor supplying combustion gas to the turbine wheel; an insert wall disposed between the combustor and the turbine wheel to provide a channel wall for the combustion gas; a nozzle vane provided between the insert wall and the nozzle ring casing to apply an aerodynamic force from the combustor to the turbine wheel; and a first band structure surrounding a portion of an outer circumference of the insert wall to prevent the insert wall from being thermally deformed and enlarged.

In an embodiment, the micro gas turbine may further include a second band structure surrounding a portion of an outer circumference of the nozzle ring casing to prevent the nozzle ring casing and the nozzle vane from being thermally deformed and enlarged.

According to the present invention, the insert wall and the nozzle ring casing are respectively surrounded in part by the first band structure of a heat resistant material and the second band structure of a material that is identical or similar to the material of the first band structure to prevent thermal deformation of the insert wall and of the nozzle ring casing and the nozzle vane so as to maintain constant gaps between the blade tip of the turbine wheel and the insert wall and between the leading edge of the turbine wheel and the nozzle vane, thereby preventing reduction in both the power output of the turbine wheel even after a prolonged drive period and the operation efficiency of the micro gas turbine.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the present invention will be more clearly understood from the following detailed description when taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a detailed front view showing a core of a conventional micro gas turbine;

FIG. 2 is a detailed cross-sectional view of the core of the conventional micro gas turbine;

FIG. 3 is a heat-distribution chart showing the thermal-deformation directions at the core of the conventional micro gas turbine;

FIG. 4 is a partially enlarged view explaining the thermal-deformation directions;

FIG. 5 is a front view showing a micro gas turbine having a band structure according to a preferred embodiment of the present invention;

FIG. 6 is a cross-sectional view of FIG. 5; and

FIG. 7 is a conceptual view showing the process of thermal deformation and enlargement occurring in a conventional micro gas turbine.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in greater detail to a preferred embodiment of the invention, an example of which is illustrated in the accompanying drawings. Wherever possible, the same reference numerals will be used throughout the drawings and the description to refer to the same or like parts. In the following description, it is to be noted that, when the functions of conventional elements and the detailed description of elements related with the present invention may make the gist of the present invention unclear, a detailed description of those elements will be omitted. However, it should be understood that the embodiment of the present invention may be changed to a variety of embodiments by those skilled in the art and the scope and spirit of the present invention are not limited to the embodiment described hereinbelow.

FIG. 5 is a front view showing a micro gas turbine having a band structure according to a preferred embodiment of the present invention, and FIG. 6 is a cross-sectional view of FIG. 5.

Referring to FIGS. 5 and 6, the micro gas turbine having the band structure according to the present invention includes a nozzle ring casing 1, a bearing casing 2, a combustor 3, a turbine wheel 4, a nozzle vane 5, an insert wall 6, a first band structure 10, and a second band structure 20.

The nozzle ring casing 1 is mounted to and supported by the bearing casing 2.

The bearing casing 2 is provided in one side of the turbine wheel 4, and receives a main journal bearing.

The combustor 3 produces high temperature and high pressure combustion gas by mixing compressed air and fuel, and supplies the combustion gas into a space between the insert wall 6 and the turbine wheel 4.

The turbine wheel 4 is driven by the high temperature and high pressure combustion gas to rotate a shaft. The rotating force of the shaft is transmitted to a electric generator (not shown) to generate electricity.

The nozzle vane 5 is provided between the insert wall 6 and the nozzle ring casing 1 so as to apply an aerodynamic force from the combustor 3 to the turbine wheel 4.

The insert wall 6 is provided between the combustor 3 and the turbine wheel 4 to provide a channel wall for combustion gas. Here, the nozzle ring casing 1 is formed from one-piece body that consists of the nozzle vane 5 and the insert wall 6.

The first band structure 10 surrounds a portion of an outer circumference of the insert wall 6 to prevent its thermal deformation and enlargement.

FIG. 7 is a conceptual view showing the process of thermal deformation and enlargement occurring in a conventional micro gas turbine.

Referring to FIG. 7, by high temperature and high pressure combustion gas from the combustor 3, the insert wall 6 is thermally deformed and enlarged in the direction denoted by arrow. If the insert wall 6 is deformed in the arrow direction, a gap between a blade tip of the turbine wheel 4 and the insert wall 6 is excessively widened. If the gap between the blade tip of the turbine wheel 4 and the insert wall 6 is widened, the power output and thus the operation efficiency of the turbine wheel 4 are reduced.

The first band structure 10 surrounds a portion of the outer circumference of the insert wall 6 so as to prevent the deformation of the insert wall 6, thereby maintaining a constant gap between the blade tip of the turbine wheel 4 and the insert wall 6. As a result, the power output of the turbine wheel 4 cannot be reduced.

Preferably, the first band structure 10 is provided in the end side of the outer circumference of the insert wall 6 away from a compressor (not shown) as shown in FIG. 6. Referring to the heat-distribution chart of FIG. 3, the greatest thermal deformation occurs in the end side of the insert wall 6 opposite the compressor, so that the first band structure is preferably provided in the end side of the insert wall opposite the compressor in the context of preventing the deformation and enlargement.

The first band structure is formed of a heat-resistant, toughened, low-thermal expansion coefficient material. For example, the first band structure 10 may be formed of a carbon fiber.

A second band structure 20 surrounds a portion of an outer circumference of the nozzle ring casing 1 to prevent the nozzle ring casing 1 and the nozzle vane 5 from being thermally deformed and enlarged.

By high temperature and high pressure combustion gas from the combustor 3, the nozzle vane 5 of the nozzle ring casing 1 is thermally deformed and enlarged. If the nozzle vane 5 is deformed, a gap between the nozzle vane 5 and a leading edge of the turbine wheel 4 is excessively widened (see section B in FIG. 4). Also in this case, the power output and thus the operation efficiency of the turbine wheel 4 are reduced.

The second band structure 20 surrounds a portion of the outer circumference of the nozzle ring casing 1 so as to prevent the deformation of the nozzle ring casing 1 and the nozzle vane 5, thereby maintaining a constant gap between the leading edge of the turbine wheel 4 and the nozzle vane 5. As a result, the power output of the turbine wheel 4 cannot be reduced.

Preferably, the second band structure 20 is provided in the end side of the outer circumference of the nozzle ring casing 1 in the proximity of the nozzle vane 5 in the context of preventing the deformation of the nozzle vane 5. The second band structure 20 may also be formed of a material that is identical or similar to that of the first band structure.

While FIGS. 5 and 6 show that the first band structure 10 is provided together with the second band structure 20, either one may be selectively provided.

Although a preferred embodiment of the present invention has been described for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention. Therefore, it should be understood that the disclosed embodiments and figures are merely illustrative forms in all aspects, rather than limited ones, so that the technical scope of the present invention is not limited to the embodiments and figures disclosed. Accordingly, the scope of the present invention should be construed as being defined by following claims and as covering all equivalents of claims. 

What is claimed is:
 1. A band structure surrounding a portion of an outer circumference of an insert wall or a nozzle ring casing in a micro gas turbine so as to prevent the insert wall or the nozzle ring casing from being enlarged due to thermal deformation.
 2. A micro gas turbine comprising: a turbine wheel; a bearing casing provided in one side of the turbine wheel; a nozzle ring casing supported by the bearing casing; a combustor supplying combustion gas to the turbine wheel; an insert wall disposed between the combustor and the turbine wheel to provide a channel wall for the combustion gas; a nozzle vane provided between the insert wall and the nozzle ring casing to apply an aerodynamic force from the combustor to the turbine wheel; and a first band structure surrounding a portion of an outer circumference of the insert wall to prevent the insert wall from being thermally deformed and enlarged.
 3. The micro gas turbine according to claim 2, further comprising a second band structure surrounding a portion of an outer circumference of the nozzle ring casing to prevent the nozzle ring casing and the nozzle vane from being thermally deformed and enlarged. 